This invention relates to a technology for excluding the influence of stray light ascribed to lights generated by the lamp heater itself, when measuring the temperature of an object, which is heated by a lamp heater, by use of a radiation thermometer.
In a film forming step, etc. in a semiconductor manufacturing process, it is common practice to heat a wafer, as a material to be treated, by a lamp heater via a susceptor or directly, in order to maintain the wafer at a designated temperature. In the film forming step, the temperature of the wafer greatly governs the film forming rate and the characteristics of the film. Thus, control of the wafer temperature is very important. As a method for detecting the wafer temperature, the technique of measuring thermal radiation from the wafer with a radiation thermometer has been known.
In this method, however, a light receiving element of the radiation thermometer simultaneously detects not only the thermal radiation from the wafer itself, but also radiated light from the lamp heating source, posing the problem that the S/N ratio of temperature measurement cannot be fully increased. As means for solving this problem, various techniques have been proposed, but no satisfactory methods have been found out.
The present invention has been accomplished in light of the above circumstances. A first object of the invention is to provide a temperature measuring system capable of making accurate temperature measurement.
A second object of the present invention is to attain the first object in a wide temperature range.
Furthermore, a third object of the present invention is to attain the first object without complicating the configuration of an apparatus.
To attain the above objects, the present invention claims a temperature measuring system for performing temperature measurement of an object to be measured, the object being housed in a chamber so as to be heated by a lamp heating source. The temperature measuring system includes: a photodetector that detects thermal radiant light from the object to be measured; and a computing section that calculates a temperature of the object to be measured, based on an output value of the photodetector, wherein an influence exerted on the output value of the photodetector, due to arrival of the light emitted by the lamp heater at the photo detector, is stored in the computing section as a function of an input power into the lamp heater, and wherein the computing section corrects the output value of the photodetector based on the function, and determines the temperature of the object, based on the corrected value.